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<title>Frequently Asked Questions - H2O - the optimized HTTP server</title>
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<a href="index.html">H2O</a>
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<p class="description">the optimized HTTP/1.x, HTTP/2, HTTP/3 server</p>

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<h2>
Frequently Asked Questions
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<h3 id="license">What are the license terms?</h3>

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H2O is licensed under <a href="http://opensource.org/licenses/MIT">the MIT license</a>.
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Portions of the software use following libraries that are also licensed under the MIT license: <a href="https://github.com/h2o/h2o/blob/master/deps/klib/khash.h">khash.h</a>, <a href="https://github.com/h2o/h2o/blob/master/deps/picohttpparser/">PicoHTTPParser</a>, <a href="https://github.com/h2o/h2o/blob/master/deps/yaml/">libyaml</a>.
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Depending on how H2O is configured, the software links against OpenSSL or LibreSSL, both of which are <a href="https://www.openssl.org/source/license.html">dual-licensed under the OpenSSL License and the original SSLeay license</a>.
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<h3 id="design-docs">Are there any design documents?</h3>

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Please refer to the main developer's <a href="http://www.slideshare.net/kazuho/h2o-20141103pptx" target="_blank">presentation slides</a> at the HTTP/2 conference, and <a href="http://blog.kazuhooku.com" target="_blank">his weblog</a>.
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<h3 id="libh2o">How do I use H2O as a library?</h3>

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Aside from the standalone server, H2O can also be used as a software library.
The name of the library is <code>libh2o</code>.
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To build H2O as a library you will need to install the following dependencies:
<ul>
<li><a href="https://github.com/libuv/libuv/">libuv</a> version 1.0 or above</li>
<li><a href="https://www.openssl.org/">OpenSSL</a> version 1.0.2 or above<sup><a href="#note_1" id="#cite_1" title="libh2o cannot be linked against the bundled LibreSSL; see issue #290">1</sup></a></sup></li>
</ul>
In case the dependencies are installed under a non-standard path, <code>PKG_CONFIG_PATH</code> configuration variable can be used for specifying their paths.  For example, the following snippet builds <code>libh2o</code> using the libraries installed in their respective paths.
</p>

<pre><code>% PKG_CONFIG_PATH=/usr/local/libuv-1.4/lib/pkgconfig:/usr/local/openssl-1.0.2a/lib/pkgconfig cmake .
% make libh2o
</code></pre>

<p>
For more information, please refer to the <a href="https://github.com/h2o/h2o/labels/libh2o">GitHub issues tagged as libh2o</a>.
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<h3 id="issues">I have a problem.  Where should I look for answers?</h3>

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Please refer to the <a href="https://github.com/h2o/h2o/labels/FAQ">GitHub issues tagged as FAQ</a>.
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<div class="notes">
<h3>Notes:</h3>
<ol>
<li id="note_1">libh2o cannot be linked against the bundled LibreSSL; see <a href="https://github.com/h2o/h2o/issues/290">issue #290</a></li>
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